How do you know how old it is?. Dating in Geology 1) Relative dating –a) Superposition –b) Correlation 2) Numerical (absolute) dating –radiometrics

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How do you know how old it is? Slide 2 Slide 3 Dating in Geology 1) Relative dating a) Superposition b) Correlation 2) Numerical (absolute) dating radiometrics Slide 4 Slide 5 Miocene-Pliocene scallops Slide 6 Paleocene Calcareous Nannoplankton Slide 7 Permo-Triassic Conodonts Slide 8 Cretaceous Bivalves Slide 9 Neogene Calcareous Nannoplankton Slide 10 Slide 11 Slide 12 Slide 13 http://www.priweb.org/ed/ICTHOL/timescale.htm Slide 14 Stratigraphic Concepts and Terminology LithostratigraphicGroup Formation Member Bed BiostratigraphicBiozones ChronostratigraphicRocksTime Erathem Era System Period Series Epoch Stage Age Slide 15 Slide 16 MesozoicCretaceousCenomanian PaleozoicDevonianGivetian CenozoicPaleoceneThanetian Using Index Fossils Slide 17 Dating in Geology 1) Relative dating a) Superposition b) Correlation 2) Numerical (absolute) dating radiometrics Slide 18 Radiometric Dating: the basic idea A product is detectable The rate of production of that product is known Product amount is 0 (or known) at age 0 of sample Product / Rate = Time example:10g / 0.5g/yr = 20 years Slide 19 IsotopesIsotopes: elements with the same atomic number but different atomic mass (number of neutrons). Some isotopes unstable ( 40 K, 14 C; radioisotopes); others are stable ( 39 K, 41 K, 12 C, 13 C) Unstable isotopes (parent) decay to another stable or unstable isotope (daughter) Rate expressed as half-life -- time in which of radioisotopes decay. Slide 20 Slide 21 Half Lives for Radioactive Elements Radioactive ParentStable DaughterHalf life Potassium 40 Argon 40 1.25 billion yrs Rubidium 87Strontium 8748.8 billion yrs Thorium 232Lead 20814 billion years Uranium 235Lead 207704 million years Uranium 238Lead 2064.47 billion years Carbon 14Nitrogen 145730 years Slide 22 Measuring decay in half-lives Slide 23 Slide 24 ParentDaughterHalf LifeDating Range _________________________________________________________________ Carbon-14Nitrogen-145730300100-70,000 ________________________________________________________________________ Potassium-40Argon-40 Calcium-401.3 billion50,000-4.6 billion ________________________________________________________________________ Uranium-238 Lead-206 4.5 billion 10 million-4.6 billion Uranium-235 Lead-207710 million Uranium-232 Lead-20814 billion ________________________________________________________________________ Rubidium-87Strontium-8747 billion10 million-4.6 billion Slide 25 Minerals you can date Potassium 40 is found in: potassium feldspar (orthoclase) muscovite amphibole glauconite amphibole orthoclase muscovite glauconite Slide 26 Minerals you can date Uranium may be found in: zircon Slide 27 Combining Radiometric and Paleontological Dating Slide 28 Slide 29 Slide 30 Slide 31 Slide 32 Dating in Geology 1) Relative dating a) Superposition b) Correlation 2) Numerical (absolute) dating radiometrics Slide 33 http://www.priweb.org/ed/ICTHOL/timescale.htm Slide 34 Dating in Geology 1) Relative dating a) Superposition b) Correlation 2) Numerical (absolute) dating radiometrics